A semiconductor metal oxide, titanium dioxide (TiO2), is very physicochemically stable, compared to other similar metal oxides, has a band gap energy of approximately 3.2 eV, and is widely applied in the fields of energy, environment, display, fiber and medicine.
Among forms of titanium oxide (TiO2), a porous metal oxide having nanopores has a regular arrangement of pores and a large specific surface area, and thus exhibits an excellent physical property. Therefore, it is applied in various applications, for example, as a photocatalyst, an electrode for a dye-sensitive solar cell (DSSC), and a hydrogen electrode.
However, since the titanium dioxide (TiO2), which is well known as a photocatalyst, has a band gap energy of 3 eV or more, the titanium dioxide (TiO2) has a poor photocatalyst property in a visible wavelength region.
Meanwhile, titanium monoxide (TiO) has a band gap energy of approximately 2.0 eV and easily absorbs wavelengths in the visible wavelength region.
The titanium monoxide (TiO) may have a halite structure, and the titanium monoxide (TiO) having a halite structure is a material that is stable at 1250° C. or more and has a stable monoclinic system at room temperature. Thus, the titanium monoxide (TiO) having a halite structure is prepared by long-term maintenance at a high temperature and rapid cooling to room temperature. In addition, the titanium monoxide (TiO) having a halite structure may be prepared by performing laser ablation in distilled water, or through a non-equilibrium process such as mechanochemical synthesis using titanium (Ti) metal and titanium dioxide (TiO2) or laser pyrolysis of a titanium precursor (titanium isopropoxide). However, this titanium monoxide (TiO) having a halite structure prepared through the non-equilibrium process performed by applying instantaneous energy has low stability.